1. Field of the Invention
The present invention relates to a substrate processing apparatus and a substrate plating apparatus, and more particularly to a substrate processing apparatus and a substrate plating apparatus for filling a metal such as copper (Cu) or the like in fine interconnection patterns (trenches) on a semiconductor substrate, and a substrate processing apparatus for electrolyzing a surface of a substrate in a plurality of stages.
2. Description of the Related Art
Aluminum or aluminum alloy has generally been used as a material for forming interconnection circuits on semiconductor substrates. As the integrated density has increased in recent years, there is a demand for the usage of a material having a higher conductivity as an interconnection material. It has been proposed to plate a substrate having interconnection pattern trenches thereon to fill the trenches with copper or its alloy.
Various processes are known, including CVD (chemical vapor deposition), sputtering, etc. for filling interconnection pattern trenches with copper or its alloy. However, the CVD process is costly for forming copper interconnections, and the sputtering process fails to embed copper or its alloy in interconnection pattern trenches when the interconnection pattern trenches have a high aspect ratio, i.e., a high ratio of depth to width. The plating process is most effective to deposit a metal layer of copper or its alloy on a substrate to form copper interconnections thereon.
Various processes are available for plating semiconductor substrates with copper. They include a process of immersing a substrate in a plating liquid held at all times in a plating tank, referred to as a cup-type or dipping-type process, a process of holding a plating liquid in a plating tank only when a substrate to be plated is supplied to the plating tank, an electrolytic plating process of plating a substrate with a potential difference, and an electroless plating process for plating a substrate with no potential difference.
Conventional plating apparatuses for plating substrates with copper have a loading/unloading unit for placing a substrate cassette to load and unload substrates, various units for plating, for performing its supplementary process, and for cleaning and drying a plated substrate, and a transfer robot for delivering substrates between the loading/unloading unit and the various units. The loading/unloading unit, the various units, and the transfer robot are disposed in a horizontal plane. A substrate is taken out of a substrate cassette placed in the loading/unloading unit, delivered between the units, processed by the units, and thereafter returned to the substrate cassette in the loading/unloading unit.
With the conventional plating apparatus, however, various structural limitations imposed by paths to transfer substrates and paths of the transfer robot make it difficult to achieve an efficient layout of the loading/unloading unit, the transfer robot, and the various units within one facility. Another problem is that the conventional plating apparatuses suffer some maintenance problems. These drawbacks are also found in other substrate processing apparatuses, such as a polishing apparatus for chemically and mechanically polishing (CMP) substrate surfaces and the like.
Furthermore, the conventional plating apparatuses have separate units for plating, pretreating, and otherwise treating substrates, and substrates are delivered to and processed by these separate units. Therefore, the plating apparatus is considerably complex in structure and difficult to control, takes up a large installation area, and is manufactured at a high cost.
When LSI circuit interconnections are formed by an electrolytic plating process, they have a microscopic structure having interconnection widths and contact hole diameters in a range smaller than 0.15 xcexcm and an aspect ratio (ratio of depth to width) of 6 or more. For embedding interconnection trenches according to copper sulfate plating alone to form such a microscopic structure, it is necessary to finely control additives and energizing conditions in the plating process. Due to variations in formed seed layers, voids tend to be formed in bottoms and side walls of interconnections and seams are liable to be formed in central regions of interconnections, making those interconnections defective.
For embedding fine interconnections fully in corresponding trenches, it is necessary to meet both requirements for improved bottom coverage and side coverage by increasing the uniform electrodeposition capability of a plating process, and for an increased bottom-up filling capability to preferential embedding from interconnection bottoms.
One proposal for achieving both a uniform electrodeposition capability and a bottom-up filling capability is an electrolytic plating process that is carried out in two stages. According to such an electrolytic plating process, for example, a substrate is plated in a first stage according to a process of a high uniform electrodeposition capability using a complex bath for increased coverage, and then interconnection trenches in the substrate are embedded using a copper sulfate bath to which an additive to increase the bottom-up filling capability is added. The plating apparatus that is used in this process comprises two cup-type or dipping-type plating cells connected in series with each other.
As another process of embedding fine interconnections fully in corresponding trenches, there has been proposed a plating process that is performed in two stages, i.e., an electroless plating stage and an electrolytic plating stage. According to such a proposed plating process, an auxiliary reinforcing seed layer is formed on a seed layer that has been formed by sputtering, for example, according to an electroless plating process, thus well preparing the overall seed layer including the auxiliary seed layer for a subsequent process. Then the seed layer is plated according to an electrolytic plating process to embed fine interconnections reliably in corresponding trenches.
The two-stage electrolytic plating process or the plating process performed in an electroless plating stage and an electrolytic plating stage, as described above, needs to have a plurality of plating apparatuses, each having a loading/unloading unit, a plating unit, processing units, and a transfer robot, which are arranged in juxtaposed relation to each other. Since these plating apparatuses occupy a large installation space in a clean room, the clean room needs to be large in size. Those plating apparatuses are responsible for an increase in the cost of the overall system. In addition, it is complex and time-consuming to deliver substrates between the plating apparatus.
Furthermore, when an electrolytic plating process is carried out on a substrate while a surface to be plated of the substrate is facing downwardly, and an electroless plating process is carried out on a substrate while a surface to be plated of the substrate is facing upwardly, a substrate reversing machine is required between the two plating apparatuses. The required substrate reversing machine poses an obstacle to attempts to make the overall system more compact and less costly.
After a substrate has been processed by one of the plating apparatuses, the substrate is dried and placed in a wafer cassette, and then delivered to the other plating apparatus. During these subsequent steps, the plated surface of the substrate may possibly be contaminated, tending to cause a plating failure such as an embedding failure or an abnormal precipitation of plated metal in the next plating process. In the drying step, the plated surface of the substrate may possibly be oxidized.
It is a first object of the present invention to provide a substrate processing apparatus which has a loading/unloading unit, a transfer robot, and various units that can efficiently be placed in one facility, and which has an excellent maintenance capability.
A second object of the present invention is to provide a substrate plating apparatus which has a single unit of reduced size and improved controllability for plating and performing its supplementary process, and which has an excellent maintenance capability.
A third object of the present invention is to provide a substrate processing apparatus which is compact and low in cost, allows a smooth transition from one substrate processing process to another substrate processing process to be performed in a short period of time, and can provide a stable substrate processing process.
To achieve the first object of the present invention, there is provided an apparatus for processing a substrate, comprising a loading/unloading unit for placing a substrate cassette to load and unload a substrate, a substrate treating unit for treating a substrate, and a transfer robot for transferring a substrate between the loading/unloading unit and the substrate treating unit, the loading/unloading unit, the substrate treating unit. The transfer robot is installed in a single facility, and the loading/unloading unit has a rotary table which is horizontally rotatable for positioning the substrate cassette in a position to detect the substrate cassette placed in the loading/unloading unit and to remove the substrate from the substrate cassette easily with the transfer robot.
The above arrangement reduces limitations on the supply of a substrate cassette to the loading/unloading unit and the removal of substrates from the substrate cassette in the loading/unloading unit with the transfer robot, allowing the loading/unloading unit and the transfer robot to be positioned for efficient operation.
The loading/unloading unit may include two loading/unloading units positioned parallel to each other, each of the loading/unloading units having a rotary table horizontally rotatable for removing the substrate from the substrate cassette in either one of the two loading/unloading units with the transfer robot. The single transfer robot is capable of efficiently removing a substrate from a desired one of the substrate cassettes easily in the two loading/unloading units.
According to the present invention, there is also provided an apparatus for processing a substrate, comprising a loading/unloading unit for placing a substrate cassette to load and unload a substrate, a substrate treating unit for treating a substrate, and a transfer robot for transferring a substrate between the loading/unloading unit and the substrate treating unit. The loading/unloading unit, the substrate treating unit, and the transfer robot are installed in a single facility, and the substrate treating unit includes a plurality of substrate treating units disposed parallel to each other in facing relation to a side wall of the facility. When the side wall of the facility facing the substrate treating units is opened, the maintenance of the substrate treating units can easily be performed.
According to the present invention, there is also provided an apparatus for processing a substrate, comprising two substrate processing facilities each having a loading/unloading unit for placing a substrate cassette to load and unload a substrate, a substrate treating unit for treating a substrate, and a transfer robot for transferring a substrate between the loading/unloading unit and the substrate treating unit. Each of the substrate processing facilities includes a plurality of substrate treating units disposed parallel to each other in facing relation to a side wall of the substrate processing facility, and the substrate processing facilities are disposed back to back at side walls opposite to the side wall. Therefore, with the substrate treating units having good maintainability, the two substrate processing facilities can be placed closely together with no space therebetween so as to save, space. In addition, a single plating process managing device can be shared by the two substrate processing facilities.
Each of the substrate treating units may comprise a unit having a substrate treating device and a plating liquid tray, for plating the substrate.
To achieve the second object of the present invention, there is provided an apparatus for plating a substrate, comprising a substrate holder for holding a substrate with a surface to be plated thereof being oriented upwardly, an anode disposed upwardly of and closely facing the substrate held by the substrate holder, and a sealing member for sealing a space defined between the substrate and the anode and filled with a plating liquid to electrolytically plate the substrate. The substrate holder has a rotatable substrate stage and a plurality of support arms vertically disposed on a peripheral edge of the substrate stage. The support arms include a support arm positioned opposite to a support arm which faces a notch or an orientation flat of the substrate when the substrate is supported by the support arms, and a pressing finger presses the substrate inwardly.
With the above arrangement, with the substrate being gripped and held by the fixing fingers while the notched portion of the substrate is being pressed against one of the support arms, the substrate is shifted from the center of the substrate holder to an off-center position toward the notch or orientation flat in the substrate by a distance corresponding to the clearance (normally about 0.4 mm with respect to the outside diameter of the substrate) between the substrate and the substrate holder. Thus, the plating area (effective area) of the substrate that can be plated can be increased without the need for complex sealing shapes and mechanisms.
The support arms may include support arms other than the support arm having the pressing finger. Each of the other arms has a fixing finger rotatably mounted for gripping a peripheral edge of the substrate.
Each of the pressing finger and the fixing fingers may have an urging member for urging the finger in a closing direction and a vertically movable opening pin for turning the finger in an 25 opening direction against the bias of the urging member, and the opening pins are vertically movable in response to vertical movement of an opening member. The apparatus further comprises an adjusting mechanism disposed between the opening pins and the opening member, for adjusting the timing of the operation of the opening pins. When the substrate is to be held, the timing of the operation of the pressing finger may be made earlier than the timing of the operation of the fixing fingers, so that the substrate is gripped by the fixing fingers after it has been displaced to an off-center position. The substrate is thus prevented from being subjected to undue rubbing engagement.
The adjusting mechanism may comprise a larger-diameter member positionally adjustably mounted on a lower end of the opening pin, and a recess may be defined in the opening member at a position confronting the opening pin. The recess has an inside diameter greater than the outside diameter of the opening pin and smaller than the outside diameter of the larger-diameter member. The opening pin may have an externally threaded lower end with a nut threaded thereover as the larger-diameter member, and the tightened position of the nut may be adjusted to adjust the timing of the operation. With two nuts used, they remain firmly tightened against loosening.
According to the present invention, there is also provided an apparatus for plating a substrate, comprising a substrate holder for holding a substrate with a surface to be plated thereof oriented upwardly, an anode disposed above and closely facing the substrate held by the substrate holder, and a ring-shaped sealing member for sealing a space defined between the substrate and the anode and filled with a plating liquid to electrolytically plate the substrate. The sealing member includes an inward extension extending radially inwardly and having a thickness decreasing gradually in a radially inward direction, and a downwardly depending member contiguous to the inward extension and bent downwardly therefrom.
Since the sealing member may be capable of withstanding a head pressure of several mm H2O, the sealing member may be of a reduced thickness of about 0.5 mm. The sealing member thus shaped allows the substrate to have an increased plating area (effective area) without impairing its sealing capability.
A plurality of divided cathode electrodes having a plurality of protrusions projecting inwardly may be mounted on a lower surface of the sealing member. Each of the protrusions are positioned outwardly of the downwardly depending member, bent downwardly at a substantially right angle along the downwardly depending member, and have a round lower end. When the lower ends of the protrusions of the cathode electrodes are brought vertically into contact with the surface of the substrate, particles are prevented from being produced by rubbing contact. The round lower ends of the protrusions reduce the contact resistance between them and the substrate if the sealing member and the cathode electrodes are integrally mounted on a support member, then they can easily be replaced when deteriorated.
According to the present invention, there is also provided an apparatus for plating a substrate, comprising a substrate holder for holding a substrate with a surface to be plated thereof oriented upwardly, an anode disposed above and closely facing the substrate held by the substrate holder, a sealing member for sealing a space defined between the substrate and the anode and filled with a plating liquid to electrolytically plate the substrate, a movable electrode head for holding the anode, and a positionally adjustable stopper having a stopper surface for abutment against a peripheral edge of the substrate for positioning the anode and the substrate relative to each other.
When teaching the substrate plating apparatus, a fixing stopper is vertically adjusted in order to make the anode parallel to the substrate when the electrode head abuts against the stopper surface of the fixing stopper. In this manner, the accuracy with which to position the electrode head repeatedly is increased, and a different electrode head used to replace the old electrode head can quickly be adjusted in position for making the current density on the substrate uniform.
The apparatus may further comprise a plurality of stopper rods extending vertically and disposed around the substrate holder. The stopper has a plurality of bolts threaded in respective nuts fixed to the stopper rods, and the bolts have upper surfaces serving as the stopper surface.
According to the present invention, there is also provided an apparatus for plating a substrate, comprising a substrate holder for holding a substrate with a surface to be plated thereof oriented upwardly, an anode disposed above and closely facing the substrate held by the substrate holder, a sealing member for sealing a space defined between the substrate and the anode and filled with a plating liquid to electrolytically plate the substrate, a movable electrode head for holding the anode, and a plating liquid tray disposed in a range which can be reached by the electrode head. At least a portion of the electrode head and the plating liquid tray for contact with the plating liquid is made of a material of poor wettability. Therefore, the plating liquid in the plating liquid tray which has a large area of contact with the atmosphere is prevented from precipitating copper sulfate on liquid-contact portions of the plating liquid tray and the electrode head, and from allowing nuclei to grow into larger solid crystals.
A dummy cathode may be detachably disposed in the plating liquid tray. When the plating liquid is supplied to the plating liquid tray and the dummy cathode is plated by an electric current passing through the anode in the plating liquid, conditioning of the anode can be performed. The dummy cathode may be made of oxygen-free copper.
According to the present invention, there is also provided an apparatus for plating a substrate, comprising a substrate holder for holding a substrate with a surface to be plated thereof oriented upwardly, an anode disposed above and closely facing the substrate held by the substrate holder, and a sealing member for sealing a space defined between the substrate and the anode and filled with a plating liquid to electrolytically plate the substrate. The plating liquid remaining in a region of an upper surface of the substrate held by the substrate holder, which is surrounded by the sealing member, is drawn and retrieved at a position on a peripheral edge of the substrate close to the sealing member while the substrate is rotating.
The plating liquid remaining on the upper surface of the substrate after it is plated is forced toward the sealing member on the peripheral edge of the substrate under centrifugal forces produced when the substrate is rotated, and hence can efficiently be retrieved at a high rate from the peripheral edge of the substrate. Therefore, the plating liquid which is expensive may be replenished less frequently, and the burden on the draining of the plating liquid may be reduced.
According to the present invention, there is also provided an apparatus for plating a substrate, comprising a substrate holder for holding a substrate with a surface to be plated thereof being oriented upwardly, an anode disposed upwardly of and closely facing the substrate held by the substrate holder, and a sealing member for sealing a space defined between the substrate and the anode and filled with a plating liquid to electrolytically plate the substrate. Rinsing pure water is supplied to a region of an upper surface of the substrate held by the substrate holder, which is surrounded by the sealing member, to clean the sealing member, and cleaning pure water is supplied to further clean the sealing member after the sealing member is separated from the upper surface of the substrate held by the substrate holder. Each time a plating process is performed, the sealing member and the cathode electrodes disposed near the sealing member are cleaned. Thus, the components that are consumed can have an increased service life.
According to the present invention, there is also provided an apparatus for plating a substrate, comprising a substrate holder for holding a substrate with a surface to be plated thereof oriented upwardly, an anode disposed above and closely facing the substrate held by the substrate holder, and a sealing member for sealing a space defined between the substrate and the anode and filled with a plating liquid to electrolytically plate the substrate. A predetermined amount of plating liquid is supplied in a single shot to the sealed space. The amount of plating liquid required for plating the substrate is small, and can be supplied quickly and reliably in one shot.
According to the present invention, there is also provided an apparatus for plating a substrate, comprising a substrate holder for holding a substrate with a surface to be plated thereof oriented upwardly, an anode disposed above and closely facing the substrate held by the substrate holder, and a sealing member for sealing a space defined between the substrate 10 and the anode and filled with a plating liquid to electrolytically plate the substrate. A plurality of treating steps are prepared, each of which can be set to use or non-use.
With the above arrangement, only one apparatus may be arranged to perform a pretreating step, a plating step, a coarse cleaning step, a main cleaning step, and a drying step, and any of these steps may be skipped. The apparatus can thus be used as a cleaning machine or a spin drying machine.
To achieve the third object of the present invention, there is further provided an apparatus for processing a substrate, comprising a substrate holder for holding a substrate, a first substrate treating head for treating a surface of the substrate held by the substrate holder according to a first-stage substrate treating process, and a second substrate treating head for treating the surface of the substrate held by the substrate holder according to a second-stage substrate treating process. Since the two substrate treating heads for performing the first-stage substrate treating process and the second-stage substrate treating process are provided, two different substrate treating processes can be performed on a single cell.
Each of the first-stage substrate treating process and the second-stage substrate treating process may comprise a substrate plating process one of the first-stage substrate treating process and the second-stage substrate treating process may comprise an electrolytic plating process, and the other comprises an electroless plating process. Alternatively, the first-stage substrate treating process and the second-stage substrate treating process may comprise respective processes for electrolytically plating the substrate with different plating liquids.
If each of the substrate treating processes is an electrolytic plating process, then an electrolytic plating liquid used in the first-stage substrate treating process may be, but should not be limited to, a copper pyrophosphate bath or a complex bath with EDTA added. Those baths with a high overvoltage are effective. An electrolytic plating liquid used in the second-stage substrate treating process may be a copper sulfate bath.
According to the present invention, there is also provided an apparatus for processing a substrate, comprising a substrate holder for holding a substrate, a first substrate treating apparatus having a first substrate treating head for treating a surface of the substrate held by the substrate holder according to a first-stage substrate treating process, and a second substrate treating apparatus having a second substrate treating head for treating the surface of the substrate held by the substrate holder according to a second-stage substrate treating process. The first substrate treating apparatus and the second substrate treating apparatus are disposed in a single facility.